Introduction to the Modern Eruv

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Eruvin: The Streets, the Strings, and the Shabbat
Rabbi Hershel Schachter

Introduction to the modern day eruv

In order to permit carrying from one domain to another or within a public domain on Shabbat, a symbolic enclosure of the area, colloquially known as an eruv, needs to be erected. In terms of halakhah, there are three elements necessary to convert a public domain into a private one. The most significant one is a border enclosing the area, whether it is a house, neighborhood, or city. The other elements are a joint partnership between the tenants of the area in the ownership of some food—which usually takes the form of a box of matzah in the local synagogue—and a deed of rental of the area from the local government. The technical term eruv, as it appears in the gemara, refers to the food which the tenants jointly own; colloquially, however, it refers to the borders of the enclosure, which is usually the most recognizable element of this legal mechanism as well as the hardest to construct.[1]

In its ideal form, the borders of an eruv would be solid walls. Of course, considering that this possibility is highly impractical in modern society, another approach needs to be investigated. The gemara introduced the concept of using tzurot ha-petah (symbolic doorways) as a wall. According to the gemara, the construction of a doorway requires two doorposts and a lintel sitting on top of the doorposts. Whereas the doorposts have certain requisite measurements, the lintel on top can be as thin as a wire or string. By lining up a number of tzurot ha-petah made of these doorposts and lintels, it becomes feasible to erect a complete enclosure of a large city. Even though using tzurot ha-petah may be the only practical option in order to construct an eruv, there is one significant caveat to this approach.

Explanations of the tzurat ha-petah enclosure

From a biblical perspective, there are two well-defined types of domains: reshut ha-yahid (a private domain) and reshut ha-rabbim (a public domain). Any other area is considered a makom patur (an exempt area). The definition of a reshut ha-yahid is an area with the minimum measurement of 4 tefahim by 4 tefahim[2] that is surrounded by walls of 10 tefahim high. A reshut ha-rabbim, on the other hand, is a street that is at least 16 ammot2 wide. An open field, then, which is neither enclosed nor used by the public, is considered a makom patur on a biblical level. The biblical prohibition of carrying an item from one domain to another only applies to from a reshut ha-yahid to a reshut ha-rabbim or vice versa. Carrying between a makom patur and a reshut ha-rabbim, or between a makom patur and a reshut ha-yahid, would be permitted on a biblical level. To avoid inadvertent violations of Shabbat, however, the rabbis introduced a fourth type of domain called a karmelit. This category includes some areas that would be considered a reshut ha-yahid on a biblical level and some areas that would be considered a makom patur on a biblical level. Continuing with our example, while an open field is a biblical makom patur, on a rabbinic level it is a karmelit. The rabbis forbade carrying from a karmelit to a reshut ha-yahid or reshut ha-rabbim. In effect we treat a karmelit like a “public domain” on a rabbinic level. [3]

Although Orthodox Jews generally observe rabbinic enactments with the same zeal as they would observe biblical commandments, the laws of eruvin demonstrate an exception to that principle; significant leniencies are based on the fact that many of its details are only rabbinic in nature. There is a general assumption amongst the poskim (rabbinic authorities) that an enclosure created by several tzurot ha-petah would not be sufficient to circumvent a biblical prohibition against carrying on Shabbat. Only once the area can be determined to be a makom patur—an area from which carrying to a reshut ha-yahid or reshut ha-rabbim entails a rabbinic, and not biblical, prohibition—can the construction of an eruv using the tzurat ha-petah ensue. In other words, a tzurat ha-petah is effective as long as one can be sure that the area is not a true reshut ha-rabbim. There are two reasons offered for this assumption.

Rabbi Yosef Teomim, author of an important commentary on the Shulhan Arukh called the Pri Megadim, raised the possibility that the tzurat ha-petah is only effective in enclosing an area according to rabbinic law. According to biblical law, however, the tzurat ha-petah is ineffective. Subsequently, using a tzurat ha-petah to enclose an area that is considered to be a “public domain” on a biblical level would simply be an insufficient means to convert it into a “private domain.” A karmelit, however, is considered a makom patur on a biblical level and is only considered “public” by the rabbis; thus by erecting a rabbinically sanctioned enclosure, one successfully converts it into a “private domain.”[4]

The Hazon Ish, Rabbi Avraham Karlitz, however, strongly disagreed with the Pri Megadim’s idea. He proved from the gemara that a tzurat ha-petah certainly functions as a wall on a biblical level. The gemara states that in order to avoid kil’ayim, the prohibition of planting two different kinds of seeds together, one may construct a tzurat ha-petah to divide between the two patches of plants. Therefore, Rabbi Karlitz concluded that the construction of a tzurat ha-petah serves as a wall even where the wall fulfills a biblical requirement.[5]

In order to defend the Pri Megadim, some later authorities suggested that there is room to distinguish between the wall that is necessary to permit carrying on Shabbat and the wall necessary to separate plants of different species. The walls in the realm of kil’ayim serve merely as a divider between two areas and as such the tzurat ha-petah accomplishes this task even on a biblical level. To permit carrying on Shabbat, however, the borders of a “private domain” need to encircle it and make it noticeably differentiated from its surroundings.[6]

Another approach in explaining the basis for limiting the use of a tzurat ha-petah enclosure to a karmelit emerges from a comment of Tosafot.[7] The gemara explains that all opinions agree that a “flimsy barrier” cannot serve as a partition if there is traffic that regularly crosses that barrier, but a “sturdy barrier” functions as a partition even if traffic passes through it. Tosafot commented that if an area is enclosed on three sides and only requires a wall on the fourth side on a rabbinic level, even if the fourth wall is “flimsy” and traffic passes through it, it nonetheless serves as a valid partition. The Maharam of Rotenberg extended the idea of Tosafot to say that in any situation that only requires a wall on a rabbinic level in order to permit carrying, that wall could be “flimsy” and is nevertheless not nullified by the fact that traffic passes through it. Based on the leniency of the Maharam, classical poskim assume that a tzurat ha-petah acts as a “flimsy wall” which functions as a partition if the area is only considered a “public domain” on a rabbinic level. Therefore, the consensus of poskim is that a tzurat ha-petah only permits carrying in the enclosed area if the area would have otherwise only been a biblical makom patur.[8]

Determination of a reshut ha-rabbim

How does one decide whether any given area is biblically considered a “public domain”? The gemara derived the 39 melahot (principal categories of labor) prohibited on Shabbat from the significant activities done in the construction of the mishkan (Tabernacle) in the desert. The gemara implicitly assumed that the transportation of the mishkan was also included in the mitzvah of constructing the mishkan. Therefore, the details of the prohibition against carrying on Shabbat can be derived from how the mishkan was transported in the desert. The wagons containing the parts of the mishkan could only have traveled on streets with a minimum width of 16 ammot; thus in order for any area to be considered a “public domain” it must include a street at least 16 ammot wide.[9] However, in practice, this definition doesn’t help very much since in almost all places where an eruv is desired, the streets are wider than 16 ammot.

One of the potential considerations in determining whether a particular area is a reshut ha-rabbim is the size of its population. Again, this criterion is based on the derivation of the laws of carrying on Shabbat from the transportation of the mishkan in the desert. Rashi and Tosafot wrote that just like there were 600,000 people in the Jewish camp in the desert, the definition of a public domain for the purposes of the prohibition of carrying on Shabbat requires a minimum population of 600,000.[10] There is a dispute as to whom is included in the count of population when determining the status of an area. The opinions range between counting all residents, counting all people who roam the streets of the area, and counting just the people who walk on a particular street.[11] Based on this assumption, many communities in Eastern Europe relied on a local eruv, considering their small villages and towns to be a makom patur (and not a “public domain”) on a biblical level.

Ramban[12] explained that the opinion of Tosafot which required a minimum population of 600,000 is limited to streets within a city. For a local street within the city to be considered public, it requires a certain level of usage. In contrast, a highway from one city to another, wrote Ramban, is automatically considered a public domain even without any minimum population simply by its definition as a major public road. It is possible to suggest that Ramban actually defined the biblical reshut ha-rabbim as a highway, and he viewed all of the guidelines about determining whether a given area is a reshut ha-rabbim as a test of whether it is sufficiently similar to a highway or not.

Some rabbis felt that this approach of Rashi and Tosafot in defining a public domain was well-accepted and served as a basis for the modern eruv.[13] Others, however, argued that many rishonim (medieval rabbinic authorities) disregarded the idea of Rashi and Tosafot and assumed that there was no minimum population for an area to be considered a reshut ha-rabbim.[14] Therefore, other suggestions were offered in order to explain the basis for local eruvin in Eastern Europe. The Arukh HaShulhan interpreted a passage in the Yerushalmi to mean that a “public domain” is defined as a street that is known to be the main street of the town. If there are multiple main streets in town, however, no one of them can be identified as a reshut ha-rabbim. Accordingly, the larger the city, the more likely it would be for the multiplicity of streets to cause there to be no particular main street.[15] Yet, the inference of the Arukh HaShulhan has traditionally been considered counter-intuitive and has not been accepted.

Another approach to defend the practice of local eruvin in Eastern Europe was that of Rabbi Shlomo Dovid Kahana. Rabbi Kahana wrote that a reshut ha-rabbim needs to be a street that passes from one end of the city to the other without making any significant turns (mefulash). If, however, the main street turns at a right angle or comes to a dead end, the area is considered a makom patur on a biblical level. Using this same approach, it is again the case that the larger the city the more likely it is to be a makom patur because of the increased likelihood that there will not be any streets which pass straight through the city. While Rav Moshe Feinstein disagreed with this leniency, Rav Moshe’s own original interpretation of this requirement (mefulash) is not generally accepted.[16]

It seems reasonable to propose, based on the Ramban mentioned earlier, that a highway that passes through a city is automatically considered a “public domain” by its definition as a public road. Therefore, a highway is not subject to the criterion of passing straight through the city in order to be considered a “public domain.” Whereas intracity streets are not considered “public” if they turn or come to a dead end, highways are “public” by definition, irrespective of whether they twist or turn.

The Hazon Ish’s model of a citywide eruv

The last major approach to explain how a large city could not be considered a biblical reshut ha-rabbim was elucidated by the Hazon Ish.[17] The gemara establishes that a border which is made up of a number of walls with gaps between them can be considered one long wall if the combined length of its gaps is less than the combined length of the standing walls. This rule is limited to cases in which each gap is less than 10 ammot in length; a wall with gaps greater than 10 ammot is not considered to be an effective border. While the Mishkenot Yaʻakov interpreted this to mean that a wall which has gaps greater than 10 ammot is not considered a “wall” even on a biblical level, the generally accepted view is that of the Beit Efrayim who argued that this would be an effective border on a biblical level, and is only invalid rabbinically.[18]

In major cities such as New York City, it is quite common to have buildings line both sides of the streets without any gaps between buildings, creating a “border” of sorts. Even if each cross street creates a gap in the continuity of the buildings, the majority of such a border would be standing walls and would only have a minority of gaps. Any street that has such buildings on both of its sides can be considered enclosed by two walls on a biblical level, since the buildings form a wall with the majority standing. Lastly, if such a street comes to a dead end where it is met by another wall of buildings, it would then be enclosed by three walls which would make it a biblical reshut ha-yahid!

Hazon Ish Diagram All diagrams are aerial views. Street A, which comes to a dead end and is lined with buildings on both of its sides, can be considered a biblical reshut ha-yahid because both its sides have a border made up of a majority of standing walls. The Hazon Ish would then proceed to explain that the imaginary lines drawn to complete the closure of Street A serve as a third partition for Streets B, C, and D which would then also become biblical “private domains.”

Before expanding this proposition, let us analyze one of our basic assumptions that the buildings that line the streets can serve as a wall for an eruv. The gemara states that a mehitzah (partition) can serve as a wall for an eruv even if it was not originally intended to be used as an eruv wall when it was constructed. Therefore, the Hazon Ish presumed that the buildings which lined the streets could serve as an eruv wall to enclose the street. R. Moshe Feinstein, however, found it difficult to view the walls of a building as a partition that would enclose the street, since they were originally constructed for the purpose of enclosing the inner part of the building and never functioned as a border of the street. Nonetheless, the gemara clearly seems to indicate that the Hazon Ish’s position is correct.[19]

With that in place, it is possible to take the Hazon Ish’s approach one step further. He said as long as it was possible to find one street that came to a dead end in a city, the rest of the city could be considered a reshut ha-yahid. According to his explanation, the street which comes to a dead end is considered a reshut ha-yahid since both of its sides are lined with buildings and at one end it comes to a dead end. In envisioning the sides of that street as walls, we can view even the gaps in the buildings—i.e. the cross streets—as forming a part of the wall, since a majority of the wall is standing. Now that the junctions between our original dead end street and its cross streets are considered a border, the cross streets become dead ends as well and each one would itself be considered a biblical reshut ha-yahid. By continuing to find the adjacent cross streets from any of these previously determined “private domains,” it is possible for the entire city to be considered a reshut ha-yahid. It is noteworthy, though, that this last extension of the Hazon Ish’s approach is questionable and its correctness can be investigated further.[20]

Formation of a tzurat ha-petah

The basic idea of a tzurat ha-petah is that it resembles a doorframe, which consists of two doorposts and a lintel on top. The doorposts need to be sturdy enough to support a lightweight door that would reasonably be used as a real door in that part of the world and whose width extends from one doorpost to the other (although it only needs to be 10 tefahim in height). The farther the doorposts are from one another, the sturdier they have to be in order to support a door that would extend from one post to the other. In actuality, very often the poles of a modern eruvin are too wobbly to realistically hold any door, calling into question the validity of these eruvin.[21]

Regarding the lintel, the Shulhan Arukh followed the version of the Talmud Yerushalmi that allows the lintel to be as thin and weak as a string. The Me’iri, however, had a version of the Yerushalmi that required the lintel to be strong enough to be able to bolt the door into it for further support. Until today, we follow the Shulhan Arukh and allow a string as the lintel.[22]

The gemara established that a tzurat ha-petah which is poorly constructed in the eyes of a professional architect is invalid. For example, the string serving as a lintel must pass directly over the top of the doorposts and may not be tied around the side of the doorposts; otherwise it is considered “poorly constructed.”[23] Similarly, if the doorposts do not touch the ground, even if they are within three tefahim of it, the Hazon Ish considered this “poorly constructed” and therefore invalid. Although there is a concept of lavud, a principle that supposes any two objects within three tefahim of one another to be considered as though they were touching, the Hazon Ish felt that it may not be employed in construction of a tzurat ha-petah since a non-Jewish architect would never use it.[24]

Diagram #2. The bottom, left, and right sides are valid borders and the fourth side is completed with a tzurat ha-petah. However, the doorposts for the tzurat ha-petah are misaligned, with one to the right and one to the left of where the wall should have been.

Another case in which a tzurat ha-petah is invalid is where the doorposts are misaligned with the gap in the border that this tzurat ha-petah would complete. For example, a tzurat ha-petah may not serve as a fourth wall of a boundary if its doorposts are to the left or the right of where the fourth wall should be (see diagram #2).[25] Additionally, if the doorpost for a tzurat ha-petah is inside of a separate reshut ha-yahid, the doorframe is invalid. This situation is possible when one of the doorposts is found inside of a fenced area (see diagram #3).[26]

Diagram #3. The black lines represent complete walls and the gray lines represent a tzurat ha-petah. One of the tzurat ha-petah poles is inside of a private domain.

In conclusion, in order to be able to construct an eruv that would permit one to carry on Shabbat, one first must clarify that the area under discussion is biblically a makom patur and not a reshut ha-rabbim. It is possible for the area not to be considered a “public domain” on a biblical level either because it lacks a population of 600,000 people, because its main street does not go straight through the city, or because buildings line the streets such as the case may be in a large city. Once the area is ascertained to be a karmelit, which is a makom patur on a biblical level, it is possible to erect an eruv using tzurot ha-petah. Finally, even if a community has a properly constructed eruv, its residents must ensure that they only use it in accordance with the rest of hilkhot Shabbat.[27]


  • This article is reprinted with permission from Eruv And Halacha pp. 47-57.
  • For practical laws of building an eruv, see the Hotzah page.


  1. The basic requirements of an eruv can be found in Rambam, Mishneh Torah, Hilkhot Eruvin 1:1-7 and 2:10 and Shulhan Arukh Orah Hayyim 366:1 and 382:1.
  2. A tefah, or handbreadth, is a measure of length between 3 and 4 inches. An ammah, or cubit, is a measure of length between 18 and 24 inches.
  3. Shabbat 6a, Rambam Hilkhot Shabbat 14:1-7, Shulhan Arukh Orah Hayyim 345, Shulhan Arukh ha-Rav 345:19, Mishna Brurah (Introduction to 345), Arukh ha-Shulhan Orah Hayyim 345:1.
  4. Bi’ur Halakhah 362:10 s.v. ke-she-kol cites the opinion of the Pri Megadim. See also Bi’ur Halakhah 364:2 s.v. ve-ahar.
  5. Hazon Ish Orah Hayyim 70:13.
  6. An elaboration of this topic can be found in Rabbi Hershel Schachter’s Be-Ikvei ha-Tzon, Siman 13:1.
  7. Tosafot Eruvin 22a s.v. kashya.
  8. Mordekhai, Eruvin Remez 509. See further in Rabbi Hershel Schachter’s article titled “The Laws of Eruvin—An Overview,” The Journal of Halacha and Contemporary Society 5 (1984): 131-150.
  9. Shabbat 99a
  10. The discussion of the opinion of Rashi and Tosafot as well as the dissenting opinions can be found in Tur and Shulhan Arukh Orah Hayyim 345:7. In the Torah’s census of the Jewish people, there were found to be slightly over 600,000 men between the ages of 20 and 60. While this number does not include women, children, elderly, and converts, Tosafot (Eruvin 6a s.v. keitzad) concluded that we can only define a “public domain” based on a number that the Torah states explicitly.
  11. Mishna Brurah 345:24, R. Moshe Feinstein in Iggerot Moshe Orah Hayyim 1:139.
  12. Eruvin 59a. See further in Rabbi Hershel Schachter’s article titled “Be-Inyan ha-Eruv be-Manhattan” in Kol Tzvi v. 7.
  13. Taz Orah Hayyim 345:6, Arukh ha-Shulhan Orah Hayyim 345:18
  14. Mishkenot Yaʻakov Orah Hayyim 120.
  15. Arukh ha-Shulhan Orah Hayyim 345:19-25.
  16. Rav Moshe Feinstein in Iggerot Moshe Orah Hayyim 5:28:6 understood the requirement of having a main street pass from one end of the city to the other as referring to the fact that every part of the street needs to have the dimensions of a public alleyway. He assumed that if one section was roofed or narrower than 16 ammot wide, the entire street could not be considered as “a public domain.” See also Iggerot Moshe Orah Hayyim 140.
  17. Hazon Ish Orah Hayyim 107:7. Most of his approach is clearly based on the gemara and earlier rabbis. However, this approach is nonetheless attributed to the Hazon Ish because one aspect of his understanding was at odds with that of Rav Moshe Feinstein. See further in Be-Ikvei ha-Tzon, Siman 13:5.
  18. Mishkenot Yaʻakov Orah Hayyim 121, Beit Efrayim Orah Hayyim 25.
  19. See Eruvin 15a and Shulhan Arukh Orah Hayyim 362:3.
  20. Be-Ikvei ha-Tzon Siman 13.
  21. Eruvin 11b, Shulhan Arukh Orah Hayyim 362:11.
  22. Meiri Eruvin 2a and footnote 64 in the Mossad ha-Rav Kook Edition by Rav Simcha Zissel Beroida; Shulhan Arukh Orah Hayyim 362:11; Bi’ur ha-Gra ibid.
  23. Even though the Taz Orah Hayyim 362:4 was lenient if the string is tied towards the top of the doorpost, his opinion has not been accepted (Mishna Brurah 362:64). Additionally, the Maharsham’s opinion that this halakhah doesn’t apply nowadays (Maharsham 1:162) is a nuance not accepted by the Mishna Brurah.
  24. Even though the Shaʻarei Teshuvah 363:4 and Steipler in Kehillat Yaʻakov on Eruvin Siman 6 assumed that this was acceptable, the Hazon Ish Orah Hayyim 71:11 and 79:11 found this invalid because it does not form a normal doorframe in the eyes of an architect.
  25. The Steipler in Kehillat Yaʻakov ibid. based upon Rabbeinu Yehonatan’s commentary on the Rif and Hazon Ish Orah Hayyim 70:16-7 agreed that the tzurat ha-petah is ineffective if the doorposts of the tzurat ha-petah are not in line with the breach in the wall. Regarding the contradictory rulings of the Hatam Sofer on this matter, see Be-Ikvei ha-Tzon Siman 12.
  26. Rabbi Yaʻakov of Lissa in Tikkun Eruvin s.v. od ra’iti she-tohavin, Avnei Neizer Orah Hayyim 290
  27. One example is playing ball on Shabbat. Even if there is an eruv, there are issues involved with playing ball on Shabbat including wearing improper clothing for the sanctity of Shabbat and nullifying the positive mitzvah of “shabbaton,” spiritually resting on Shabbat. Regarding playing games on Shabbat, see Arukh ha-Shulhan Orah Hayyim 308:70 quoting from the Yerushalmi. Concerning the mitzvah of resting on Shabbat, see Rambam Hilkhot Shabbat 1:1, Ramban Vayikra 19:2, and Ibn Ezra Shemot 20:8.